Organization of the Periodic Table

Demetry Mendeleev organized the elements in the first periodic table by order of mass in Found repetition in properties of elements Found repetition in properties of elements Widely accepted because it was able to predict the existence and properties of undiscovered elements Widely accepted because it was able to predict the existence and properties of undiscovered elements elements were being placed in groups of elements with differing properties Problem: elements were being placed in groups of elements with differing properties

In 1913 Henry Mosley, an English Chemist, reorganized the Periodic Table based on the number of protons. Clear periodic patterns Clear periodic patterns Mendeleev’s problems of properties are solved Mendeleev’s problems of properties are solved – there is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number Periodic law – there is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number

The Modern Periodic Table

Elements are placed on the Periodic Table based on the number of protons in their nucleus

Families

Each element in a particular family contains the same number of outer shell electrons, or valence electrons.

Families Each family is followed by the letter A or B. Each family is numbered 1 through 8, followed by the letter A or B. The families designated with an because they possess a wide range of chemical and physical properties. The families designated with an A (1A-8A) are called representative elements because they possess a wide range of chemical and physical properties. Families designated with a are referred to as Families designated with a B are referred to as transition elements.

Periods

Other major divisions in the Periodic Table include the metals, nonmetals, and metalloids

Metals

Characteristics of Metals Shiny and smooth Shiny and smooth Solid at room temperature Solid at room temperature Good conductors of heat and electricity Good conductors of heat and electricity Ductile and malleable Ductile and malleable Most group A and all group B elements are metals Most group A and all group B elements are metals Group 1A elements (except H) are Group 1A elements (except H) are alkali metals Group 2A elements are alkaline earth metals; both are chemically reactive, alkali the more reactive struck by e- Elements from group B (lanthanide series) are used as phosphors, substances that emit light when struck by e-

Nonmetals

Characteristics of Nonmetals Upper right side of periodic table Upper right side of periodic table Gases or brittle Gases or brittle Dull-looking solids Dull-looking solids Poor conductors of heat and electricity Poor conductors of heat and electricity Br – only nonmetal that is a liquid at room temp. Br – only nonmetal that is a liquid at room temp. Halogens – 7A, highly nonreactive 8A, extremely nonreactive Noble gases – 8A, extremely nonreactive

Metalloids

Characteristics of Metalloids Physical and chemical properties of both metals and nonmetals Physical and chemical properties of both metals and nonmetals Silicon and Germanium are two of the most important metalloids, they are Silicon and Germanium are two of the most important metalloids, they are used in computer chips and solar cells

Silicon – used in computer chips and solar cells

Atomic Radius How closely an atom lies to a neighboring atom How closely an atom lies to a neighboring atom Trends within periods = decrease due to outermost e- being pulled toward nucleus Trends within periods = decrease due to outermost e- being pulled toward nucleus Trends within groups = increase due to shielding and increased energy levels Trends within groups = increase due to shielding and increased energy levels Atomic radius

Atomic Radius

Ionic Radius Ion=atom that has a + or – charge due to the gain or loss of e- Ion=atom that has a + or – charge due to the gain or loss of e- Lose e-/ + charge / smaller atom - electrostatic repulsion decreases & valence e- leaves unfilled orbital Lose e-/ + charge / smaller atom - electrostatic repulsion decreases & valence e- leaves unfilled orbital Gain e-/ - charge / larger atom – electrostatic repulsion increases & causes increase distance between outer e- causing larger radius Gain e-/ - charge / larger atom – electrostatic repulsion increases & causes increase distance between outer e- causing larger radius Ionic radius

Ionic radii Trends within periods = size of the + ion decreases, then beginning in group 5A or 6A the larger – ion decreases Trends within periods = size of the + ion decreases, then beginning in group 5A or 6A the larger – ion decreases Trends within groups = ion size increases due to the ion’s outer e- being in higher energy levels Trends within groups = ion size increases due to the ion’s outer e- being in higher energy levels

Ionization energy is the energy required to remove an electron from a gaseous state atom

Ionization Energies

Ionization energy 1 st, 2 nd, 3 rd etc. 1 st, 2 nd, 3 rd etc. How strong atom’s nucleus holds onto the valence e- How strong atom’s nucleus holds onto the valence e- Large ionization energy, less likely to form + ions Large ionization energy, less likely to form + ions Low ionization energy, atom loses outer e- easily and easily forms + ions Low ionization energy, atom loses outer e- easily and easily forms + ions

Ionization Energy Trends Trends within periods = increase due to increase in nuclear charge producing an increased hold on valence e- Trends within periods = increase due to increase in nuclear charge producing an increased hold on valence e- Trends within groups = decrease due to valence e- being farther from the nucleus requiring less energy to remove them Trends within groups = decrease due to valence e- being farther from the nucleus requiring less energy to remove them

Octet Rule Atoms tend to gain, lose, or share e- in order to acquire a full set of eight valence e- Atoms tend to gain, lose, or share e- in order to acquire a full set of eight valence e- Exception : 1 st period completely filled with 2 e- Exception : 1 st period completely filled with 2 e- Elements on the right side of the periodic table tend to gain e- and tend to form – ions Elements on the right side of the periodic table tend to gain e- and tend to form – ions Elements on the left side of the periodic table tend to lose e- and form + ions Elements on the left side of the periodic table tend to lose e- and form + ions

Electronegativity is how much atoms pull electrons away from another atom Electronegativity is how much atoms pull electrons away from another atom

Electronegativity Values

Electronegativity Trends Trends within periods = increase Trends within periods = increase Trends within groups = decreases Trends within groups = decreases Lowest electronegativities are found at the lower left side of the periodic table Lowest electronegativities are found at the lower left side of the periodic table Highest electronegativities are found at the upper right side of the periodic table Highest electronegativities are found at the upper right side of the periodic table